linux-kernel - Re: [PATCH 8/8] dt-binding: mtd: Document gpio-addr-flash

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Message-ID: <20180831121751.GA22256@bogus>
Date:   Fri, 31 Aug 2018 08:17:51 -0400
From:   Rob Herring <robh@...nel.org>
To:     Ricardo Ribalda Delgado <ricardo.ribalda@...il.com>
Cc:     David Woodhouse <dwmw2@...radead.org>,
        Brian Norris <computersforpeace@...il.com>,
        Boris Brezillon <boris.brezillon@...tlin.com>,
        Marek Vasut <marek.vasut@...il.com>,
        Richard Weinberger <richard@....at>,
        Zhouyang Jia <jiazhouyang09@...il.com>,
        linux-mtd@...ts.infradead.org, linux-kernel@...r.kernel.org,
        devicetree@...r.kernel.org
Subject: Re: [PATCH 8/8] dt-binding: mtd: Document gpio-addr-flash

On Tue, Aug 21, 2018 at 04:31:52PM +0200, Ricardo Ribalda Delgado wrote:
> Add documentation for gpio-addr-flash. This binding allow creating
> flash devices that are paged using GPIOs.
> 
> Cc: devicetree@...r.kernel.org
> Signed-off-by: Ricardo Ribalda Delgado <ricardo.ribalda@...il.com>
> ---
>  .../bindings/mtd/gpio-addr-flash.txt          | 46 +++++++++++++++++++
>  1 file changed, 46 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/mtd/gpio-addr-flash.txt
> 
> diff --git a/Documentation/devicetree/bindings/mtd/gpio-addr-flash.txt b/Documentation/devicetree/bindings/mtd/gpio-addr-flash.txt
> new file mode 100644
> index 000000000000..4279e8cad09b
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/mtd/gpio-addr-flash.txt
> @@ -0,0 +1,46 @@
> +Memory Mapped flash with some address lines addressed using GPIOs

That's ugly...

> +
> +Handle the case where a flash device is mostly addressed using physical
> +line and supplemented by GPIOs.  This way you can hook up say a 8MiB flash
> +to a 2MiB memory range and use the GPIOs to select a particular range.
> +
> + - compatible : "cfi-gpio-addr-flash"

Why a new compatible? Shouldn't just adding some address gpios to an 
existing flash device binding be sufficient?

> + - reg : Address range of the mtd chip that is memory mapped, this is,
> +   on the previous example 2MiB.
> + - bank-width : Width (in bytes) of the bank.  Equal to the
> +   device width times the number of interleaved chips.
> + - probe-type : (optional) "cfi_probe", "jedec_probe". How the mtd chip
> +   is going to be probed. If omitted, assumed to be equal to "cfi_probe".
> + - #address-cells, #size-cells : Must be present if the device has
> +   sub-nodes representing partitions (see below).  In this case
> +   both #address-cells and #size-cells must be equal to 1.
> +
> +The device tree may optionally contain sub-nodes describing partitions of the
> +address space. See partition.txt for more detail.
> +
> +Example:
> +
> +	cfi_flash_0: cfi_flash {
> +		#address-cells = <1>;
> +		#size-cells = <1>;
> +		compatible = "cfi-gpio-addr-flash";
> +		bank-width = <2>;
> +		reg = < 0x00300000 0x00200000 >;
> +		gpios = <&gpio_0 3 0>, <&gpio_0 4 0>;
> +		partition@0 {
> +			reg = < 0x0 0x200000 >;
> +			label = "Golden Bitstream";
> +		};
> +		partition@...000 {
> +			reg = < 0x200000 0x200000 >;
> +			label = "User Bitstream";
> +		};
> +		partition@...000 {
> +			reg = < 0x400000 0x200000 >;
> +			label = "V4L Controls";
> +		};
> +		partition@...000 {
> +			reg = < 0x600000 0x200000 >;
> +			label = "Production Data";
> +		};
> +	} ;
> -- 
> 2.18.0
>